Drilling for what?

The rig here is in a tiny wedge of ground between railway and road, with seemingly little practical value. So what are they drilling for? (I assume it is drilling for something.) I guess that as it is in an area where the water table is very high and flooding a risk, it may be exploratory to assess what can be done there in future.

On reflection, I wonder if it is just going to be another aerial for mobile phones.